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Divergence question

jimmy433

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Hey fellas,

so it turns out i have a few LPC-840's to experiment with, i thought i was going to be working with the 836's but nonetheless, i bought a 660nm heat sink module + host from ebay for it, i think it came with a m9x0.5mm plastic lens.

Iv attached a picture below, my question is should the beam be diverging this much?

Iv also tested the power output of these bad boys and they are horrible, i could hardly get over 300mW out of these and they are supposed to be rated at like 500mW.

Also i have tried focusing the lens by screwing it in and out but it stays pretty much the same.
 

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ZRaffleticket

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Silly question... could the lens be in backwards?

If not I'd see about replacing it with a different lens.
 
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steve001

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Hey fellas,

so it turns out i have a few LPC-840's to experiment with, i thought i was going to be working with the 836's but nonetheless, i bought a 660nm heat sink module + host from ebay for it, i think it came with a m9x0.5mm plastic lens.

Iv attached a picture below, my question is should the beam be diverging this much?

Iv also tested the power output of these bad boys and they are horrible, i could hardly get over 300mW out of these and they are supposed to be rated at like 500mW.

Also i have tried focusing the lens by screwing it in and out but it stays pretty much the same.
You haven't actually defined what you want to do. Just made us aware of your results. What do you want to do?
 

Alaskan

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Edit to soften stance:

With that LPM, the breadboard and all, I just don't see such a basic question coming to us. Possible? Yes, but I think improbable. Jimmy, tell us more about your hobby with lasers, I hardly know anyone who has a big optical breadboard like that here, sure we probably have members who have them, but that's a huge expensive one to buy new and it looks in pristine shape. What are you doing with lasers, work or hobby? If work, I'm surprised you are asking this kind of question.
 
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Rivem

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Do you have any other lenses? I've noticed absolutely terrible performance from acrylic lenses occasionally. I think they sometimes just don't have the right focal length for certain diodes and modules.
 

diachi

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I am sorry to beat the troll drum again guys, but if he took that picture and has that optical breadboard, he wouldn't be here asking this.

Edit: I don't know, I suppose it is possible, but with that LPM, the breadboard and all, I just don't see such a basic question coming to us. Possible? Yes, but I think improbable. That and all the member names with numbers popping in and disappearing, Jimmy, tell us more about your hobby with lasers, I hardly know anyone who has a big optical breadboard like that here, sure we probably have members who have them, but that's a huge expensive one to buy new and it looks in pristine shape. What are you doing with lasers, work or hobby? If work, I'm surprised you are asking this kind of question.
Good point.

Also OP, those diodes are not "rated" at 500mW, not even close. the ~400mW we push them to is already above their rating.

Have you screwed the lens all of the way out, then all of the way back in while looking at the far field dot?
 

Alaskan

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There was a member here a year or two ago who had the same problem, his lens was in backwards.
 

jimmy433

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Iv attached a picture below, my question is should the beam be diverging this much?
As i said at the start my question is should the beam be diverging this much?

what result do you/should i usually get? should it be more collimated at that distance? etc..

The lens isn't in backwards iv tried it both ways and screwed the lens in and out to almost every thread also the LDs in properly :thanks:

I think iv mentioned it before on here but basically i am to design a device with relatively cheap equipment (salvaged parts, stuff from ebay etc) which will combine the narrow band visible light of two laser diodes and implement a cheap fibre coupling method to have the combined light pass through some doped fibre optic and measure (wavelengths and power) the broadband infrared light achieved.

Its for a university project and touches on the field of spectroscopy, where the manipulation of the atmospheric transmission window of 1.5-5 micro meters is the main focus.
 
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paul1598419

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My best guess is you have a crap lens. Try to find as aspheric single element lens with a short focal length. Somewhere around 2.3mm should suffice. These can be had for less than $10.00, depending where you look. That diode is a single mode 650nm with great divergence specs, but 400 mW is about the best you can hope for with the right lens. I noticed your driver seems to be solder side down on a metal table. If so, a very bad idea.
 
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Alaskan

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That optical bread board doesn't like right under one of these cheap crappy low power laser diodes and using a cheap lens, well, when you figure it out please post.
 

steve001

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As i said at the start my question is should the beam be diverging this much?

what result do you/should i usually get? should it be more collimated at that distance? etc..

.
You appear to have a short focal length lens.
Yes it should diverge that much.
Do a crash course on optics and laser beam probagation via the web.

P.S. A rhetorical question.
Why did you take on this project and not realize you don't know a thing about optics?
 
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jimmy433

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Mate i dont know about you but 9/10 times im gona pick the only project which involves "high power lasers" out of a list of about 30 where the others are mostly coding :crackup:
 




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